This invention relates generally to marine vessels and, more specifically, to sheet or panel clad marine vessel hull construction wherein sheet skin layers are formed with differential bends and are adhesively bonded to frame members to avoid welding procedures and formation of heat affected areas. This invention also includes a unique method of constructing such a marine vessel hull.
The materials of construction for a boat hull require the combination of formability, strength, attractive appearance, low maintenance and durability in the marine environment. The boat hull has been developing for thousands of years. For a very substantial period of time boat hulls of varying sizes have been constructed of wood. Wooden hulls typically use a wooden skeleton of transverse ribs on which the planks are mounted and secured. They are made watertight by caulking with oakum, the pressure necessary for a watertight joint being produced by soaking the wood to swell it. However, wooden boat hulls disadvantageously require substantial maintenance and are subject to deterioration. In addition wooden hulls require substantial labor costs for construction and use of increasingly costly wood materials.
The next stage of development was ship hulls of steel wherein the planking, formed of three-dimensional shaped steel plates, was secured by riveting to a steel skeleton. Caulking and closely juxtaposed rivets make the joints watertight. Later, with the development of welding technology, the planks were welded in place as employed still today in modem-day construction of large boat hulls.
More recently, boat hulls have been increasingly constructed of fiberglass. Fiberglass is utilized to allow manufacturing of the hull into complex curvatures and shapes. The shape the boat hull is quite difficult to fabricate from materials such as steel or the like. Complex shapes are possible by using molds, but such molds are themselves difficult to fabricate and are very expensive, particularly for more complex shapes, such as catamaran style hulls. Fiberglass also provides a desired outer appearance in the boat, being smooth and aesthetically pleasing, and also being easily painted or otherwise decorated. At the same time, fiberglass hulls do have some disadvantages. First, fiberglass has the tendency to fracture. Moreover, fiberglass does not have as much rigidity as other materials, such as steel or an aluminum hull boat would have. Manufacturing with fiberglass materials can also be environmentally problematic. The manufacture of fiberglass can result in the release of volatile organic compounds that are distressing in both the manufacturing facilities and the immediate environment. The volatile organic compounds used in fiberglass manufacture are hazardous materials and can also be destructive to ozone in the atmosphere. In addition, fiberglass blisters, absorbs water, and requires special finishes and maintenance to protect it from the sun or other environmental conditions.
There have also been attempts at constructing larger boats with hulls made of aluminum. Unlike the fiberglass hulls, aluminum is less subject to fracturing and yet is lightweight. Although having these desirable characteristics, disadvantages of using aluminum are found in the time consuming assembly steps to achieve any complex curvatures or shapes and to obtain smoothness for cosmetics. Aluminum hulls are usually constructed by a process of forming metal sheets, for example two sheets side by side for the underwater panels, two side panel sheets joined at their front ends to a stem and along their lower edges to the underwater panels, and a sheet for the transom. The use of formed sheets generally limits the shapes achievable, particularly for large boats of eighteen feet or longer. The shapes are further limited by the requirement to form each sheet separately and precisely to match with the adjacent sheets. The sheets are then welded along the seams where they join one another, frequently along with extrusions of metal on the seams. The welding operation is one of the most expensive operations in the construction of a boat hull using aluminum. Additionally, a frame structure is then welded into place to provide structural integrity, and support for decking or other surfaces. The most commonly used metal in such construction is marine grade aluminum, which upon welding, suffers damage and/or weakening in a heat-affected zone near the weld site. This heat-affected zone is subject to cracking under fatigue loading. There are also additional problems associated with the welding. The welds can fail and are subject to oxidation. Also, the welds are typically overdesigned such that too much welding is done, unnecessarily adding to the cost and further weakening the surrounding metal. It is also necessary to have very close tolerances between the members to be welded, generally resulting in significant scrap material, and increasing costs. The heat-affected zone is also visibly altered, creating a blemish on the exterior of the hull. It is a significant drawback of aluminum boats that welding produces blemishes, such as surface disfiguration, which destroys the desired smooth appearance. Such blemishes must be cosmetically repaired, typically using a bondo type product, to yield an outer appearance as desired.
It would be of great benefit if the hull designed of aluminum could be formed from sheets, but yet allow performance enhancing compound, complex curves and shapes to be obtained, particularly for large boats of eighteen feet or longer. Similarly, it would be desirable to provide an aluminum boat with an aesthetically pleasing appearance without damage occurring from welding procedures. Additionally, it would be desirable to eliminate a significant amount of welding in forming structures of the boat, such as in attaching the support frame structure to the hull.
It is therefore an object of this invention to minimize reliance on welding by using an adhesive compound to connect frame members, decking and other structures to the hull.
It is a further object of this invention to provide a large panel built boat hull having a length of eighteen feet or greater with complex shapes and curves formed integrally therein. The boat hull may also be a catamaran style hull.
It is another object of this invention to provide a method of making a panel hull in an efficient and cost effective manner, and forming a hull having complex or differential curvatures and bends by selective and sequential bending of predesigned sheets of material. The bending procedures may be carried out repeatably by use of computer controlled brake presses, and over large lengths, to form a cost effective hull construction.
The invention is directed to a marine vessel and method of construction, wherein the vessel hull is formed to have a bottom and side portions, and includes a frame comprising a plurality of at least rib members extending crosswise and selectively fixed to the bottom or side portions of the hull. For some hull designs, particularly for larger hulls, it may also be desirable to provide stringer members, which extend longitudinally within the hull and are fixed into engagement with at least one of the bottom or side portions of the hull. The rib members extend across at least a portion of the width of the hull and are fixed to the hull to provide structural integrity. The rib members are fixed into engagement by an adhesive bond; wherein the adhesive bond provides an amount of resiliency to dampen vibrations and other forces at the location of engagement. The invention is also directed to a method of forming the hull using a plurality of sheet members, each of which is formed with a plurality of complex bends and has a compound curvature from the front to rear. The sheets are formed by imparting consecutive and sequential bends in the various sheets to form at least a part of the side and bottom portions of the hull, while concomitantly imparting a desired curvature from fore to aft. It is also an aspect of the invention that the hull design and associated structures are repeatably manufactured in a production boat rather than custom, and the designs are scalable to meet user requirements.